The present invention relates generally to the repair of heat exchangers and, more particularly, to the simultaneous straightening and insertion of tubular sleeves into the heat exchanger tubes of steam generators.
Heat exchangers which utilize a plurality of tubes to separate primary and secondary fluids and to provide thermal communication therebetween occasionally develop faults in the walls of these tubes which can lead to leakage between these primary and secondary fluids. One recognized method of repairing these flaws is to insert a tubular sleeve into the damaged heat exchanger tube in the region of the flaw and then to bond the tubular sleeve to the inside cylindrical surface of the flawed tube. However, typical heat exchanger designs usually preclude a full extension of the tubular sleeve coaxially from the end of the damaged tube prior to its insertion into it. Typically, a heat exchanger has a hemispherical end portion which contains a chamber with which the heat exchanger tubes are in fluid communication. In cases where the tubular sleeve member is longer than the maximum linear dimension available within the chamber, this method of repair is essentially proscribed since a straight sleeve must be extended coaxially from a flawed tube before being inserted into it.
Since the hemispherical end portion of this type of heat exchanger is typically divided into two generally equal portions, each resultant chamber is in the shape of a quarter section of a sphere. This shape severely limits the maximum length of a straight tube that can be effectively manipulated within the quarter-sphere and subsequently inserted into the damaged one of the plurality of heat exchanger tubes which intersect one of the flat sides of the quarter spherical chamber in a perpendicular direction.
The present invention solves this sleeve insertion problem by permitting the tubular sleeve to be in a bent condition as it is manipulated within the quarter spherical chamber in order to reduce its effective maximum linear dimension. The bent tubular sleeve is then straightened as it is inserted into the heat exchanger tube that is to be repaired. The present invention, which can both bend and straighten the tubular sleeves, can be rigidly attached to the flat surface through which the heat exchanger tubes extend and through which the sleeve must be inserted.
The present invention permits various strategies to be employed during the tube repair operation. One method comprises bending the tubular sleeve into a arcuate shape outside of the heat exchanger and then inserting the arcuately shaped tubular sleeve through a manway and into the quarter spherically shaped chamber. From there, the arcuately shaped tubular sleeve can be passed through the present invention, straightened, and simultaneously inserted directly into the flawed tube. Alternatively, in cases where significantly long tubular sleeves must be inserted into the heat exchanger tube, a long straight sleeve can be passed through the manway and curved as it enters the heat exchanger chamber although this technique is not preferred when the quarter-spherical chamber is radioactive because of the amount of manual effort required within the chamber. Alternately, if its length is significantly long, the sleeve can be bent into a helical shape outside of the chamber to minimize the volume of space required to maintain it in the chamber prior to its insertion into the heat exchanger tube to be repaired and to permit its entry through the above-mentioned manway. The helically shaped sleeve can then be passed into the chamber through the manway and through the present invention, being straightened simultaneously as it is inserted into the damaged tube. When significant bending of a tubular sleeve is required, multiple passes through the present invention may be necessitated.
The present invention provides an apparatus and method of inserting tubular sleeves into damaged heat exchanger tubes that is not limited to the relative sizes of the quarter spherical shaped chamber of a heat exchanger or the length of the tubular sleeve.